Electronic Avionics Equipment is an inseparable and necessary part of modern aircraft. Complex electronic system equipment of that type, for example, is used in radar systems that determine proximity to other aircraft or weather patterns; is used in electronic navigation systems, such as the "Loran" system, through which the aircraft position in travel may be monitored; and is used in electronic countermeasures systems, familiar in military aircraft, through which radar guided missiles may be electronically confused and diverted to shield the aircraft from harm. A characteristic of avionics equipment is that it contains many types of electronic circuits: Like most modern electronic equipment it includes digital type circuits, such as microprocessors and other computerized controllers, analogue type circuits for processing analogue signals, and RF circuits, microwave energy transmitting and/or receiving stages.
The manufacture of such modern electronic equipment involves many aspects of testing to ensure operability. Given the design of a circuit, the apparatus is assembled from electrical and mechanical components in a step by step procedure and is tested; finally being packaged in a metal container with accessible electrical connectors for connection to other systems. For example typical equipment contains one or more printed circuit boards or printed wiring board assemblies, PWBA's, as variously termed, containing sockets and inter-component connections. Electrical components such as resistors, capacitors, electrical connectors, RF oscillators, power supplies and especially a large number of integrated circuit chips are mounted to the PWBA's. Two or more of such PWBA's are often assembled into a common unit, forming a "module", that is thus of greater complexity. In turn the module is often connected with other modules, to form a system or "unit", and the unit provides even greater complexity.
To assure that the equipment functions prior to delivery to the customer considerable quality control is given to the product at the factory during production. In high quality electronic systems of the kind used in industry and the military, particularly in aircraft, testing is a necessary part of the manufacturing process and is accomplished at many stages of production. The bare PWBA's are tested; when the PWBA is "stuffed" with the electronic components, the board assembly or module is tested; and when the system is assembled from the modules, the overall system is tested. When the system is installed in its intended site, for example in an aircraft, the system is again tested, assuring performance.
As those skilled in the art appreciate testing complex electronic devices is a difficult process. In a digital circuit it involves determining whether many of thousands of functions are in fact performed and in an analogue circuit it involves determining margins and ranges of operation to complicated specifications; totally unlike switching on a light switch to see if a light bulb lights up. Beyond the manufacture and delivery, the avionics system must be tested upon installation, such as following installation in an aircraft. And thereafter the equipment must be maintained; tested occasionally to determine whether the installed equipment is performing to specification. If not, the reason for the insufficiency must be diagnosed and the necessary repair made.
A large customer of complex electronic equipment, the U.S. military as example, may procure like kinds of electronic systems from many different sources. A radar system may be purchased from one company, an electronic countermeasures system from another and a navigation system from still another manufacturer. Each of those electronic systems typically contains an RF section, a digital section and an analog section; although such electronic equipment is of like kind in a generic sense they are not identical and are not the same in a specific sense. To test the product procured from one such company test equipment must also be designed and purchased from that company which is specialized to that company's product, if customer maintenance and repair is to be sustained. Even though such specialized test equipment may contain some "off the shelf", standard, test equipment, that off the shelf equipment is modified with adapters and the like and is supplied as a test set to fit the particular test situation.
As a practical matter the one manufacturer's test set cannot be conveniently adapted for test of the product of the second manufacturer. For each such system, the customer must purchase another test set as is the present practice. Moreover the situation that exists for products purchased from different manufacturers also applies to different electronic systems purchased from the same manufacturer, as is also the present practice. The clutter of electronics test sets at customer test facilities is often awesome
Quite frequently the test set that the customer requires to maintain a given electronic system is the same test set that is used by the equipment seller's factory personnel Often the supply of a copy of the factory's test set is regarded as a cost saving measure to avoid redesign. Additional copies of the factory test sets are procured, fabricated and supplied to the customer as separate items Recognizing that the factory testing is usually more thorough and involves some kinds of tests not usually contemplated for maintenance in the field, the test set may contain more equipment and/or features than is needed, reducing the sought after cost savings. Procuring copies nonetheless remains the easiest and quickest way to obtain test sets prior to the present invention.
Although seemingly simple in concept in present practice such customer based testing efforts thus involves enormous difficulty and commitment of resources and presents unfortunate delays, involving authoring and specification of technical manuals, testing procedures, training of personnel to do the training and the design and construction of test sets with which to perform the testing Unlike the modern "throwaway" society of small inexpensively produced in high volume appliances in which when the appliance fails, it may be discarded, not repaired, and a replacement purchased, complex electronic equipment of this kind must be maintained and repaired.
An important part of test set procurement at present is the authorizing of a test document that explains the test set, the tests and the procedures for performing the tests for the customer's personnel. The cost of such documents is significant.
A real difficulty in the maintenance practice lies not only in the generation of paperwork, but in training test personnel. It is one thing for the test sets to be used by factory and operations testing personnel who built the equipment from the ground up and who used that test equipment throughout production with much of the "know how" on the test set residing only in the cranial regions of the particular factory personnel; and another totally different matter when the test set is handed to a newly inducted Air Force airman together with a 20,000 page document on the test set. However intelligent and well intentioned the airman may be, the task laid before the person is indeed formidable, if not overwhelming. As the present practice continues the delay and cost of training the customers personnel can only worsen.
With modern avionics systems, the testing technology transfer time is effectively measured in years, not months or weeks. As electronic systems become even more complex, the unfortunate trend, should present maintenance practices continue, is that the transfer of testing capability will take many more years and perhaps swallow the customers resources, dwarfing the cost of the original system installed. That is not a desirable end for advancing technology. Fortunately, the present invention changes the practice, breaks that trend and presents a new capability with which technical personnel may be trained and testing of complex electronic devices may be accomplished more efficiently.
One obvious solution to the customer's existing dilemma is to return all electronics system equipment to the factory and allow the experienced factory personnel to perform the tests. Often this is not a practical approach. Given completion of a complex system, the factory moves its personnel to new tasks and are not readily available; few customers are willing to pay for the factory to maintain personnel dedicated to that purpose. In other situations the customer requires self assurance that its required maintenance is given the priority that it dictates by having technical personnel, its own employees, at its beck and call, at any place in the world where that customer's avionics equipment may be located. In the case of military equipment the need for prompt, essentially on the spot kind of repair capability has been traditionally regarded as a necessity to military planners.
The pressure to reduce personnel training time and make testing more efficient is felt even at the factory level. By reducing the testing costs, the product may be produced at less expense and at a more predictable cost to the obvious benefit of both factory and customer alike. Should a new system be proposed to a potential customer to achieve new ends, the predicted cost is a factor in whetting the customers appetite or in dampening that appetite; the cost of testing is an integral part of the cost of the system initially. If the system cost is too high, then there is little business; if the cost is set too low the factory may incur a deficit and bankruptcy for the project. The present invention enhances the specification and accomplishment of testing in the factory environment.
Automatic test systems for testing electronic apparatus which incorporate computers and computer to computer communications systems and computerized testing have been previously explored by others. Reference to the patent literature identified herein provides additional background to the present invention: U.S. Pat. No. 4,658,400 granted Apr. 14, 1987 to Brown, et. al. for a WSI tester; U.S. Pat. No. 4,402,055 granted Aug. 30, 1983 to Lloyd, et. al. for an Automatic Test System Utilizing Interchangeable Test Devices; U.S. Pat. No. 4,760,330 granted July 26, 1988 to Lias for a Test System With Shared Test Instruments; U.S. Pat. No. 4,796,206 granted Jan. 3, 1989 to Bostove, et. al. for a computer assisted vehicle service featuring signature analysis and artificial intelligence; U.S. Pat. No. 4,707,834 granted Nov. 17, 1987 to Frisch et. al. for a computer based instrument system; U.S. Pat. No. 4,393,498 granted July 12, 1983 to Jackson et. al. for a Method and Apparatus for Testing Systems over Digital Buses by Transmitting and Receiving Signals in the Form of Standardized Multi-Bit Binary Encoded Words that uses a microcomputer adapted to test complex avionic line replaceable units; and U.S. Pat. No. 4,488,299 granted Dec. 11, 1984 to Fellhauer et. al. that presents a computerized test system for electrical Circuits.
The use of computer to computer communications for transfering test programs and data is known. Related computer systems are known in which common or shared data is to be maintained at a plurality of different computers at distinct locations in which the shared data may be entered at the one authorized location that effectively "owns" the particular information and then is automatically distributed in due course, not in real time, to update the data at each of the remote locations, are known. One such system is described in U.S. Pat. No. 4,714,995 to Materna, et. al. granted Dec. 22, 1987, assigned to the assignee of the present invention. In the Materna patent the computer systems may contain the information to be updated in databases having different formats. Nonetheless associated translating apparatus tailors the format to each respective database and the digital information is sent in proper form. Moreover at the remote location an operator may inquire of the "owning" computer for the particular data and date of last update to ensure that the latest data is on hand at the remote location before undertaking any action locally based on the information. The present invention incorporates aspects of such computer to computer communications.
An object of the present invention is to minimize the training required for technicians who must maintain such systems; to relieve that person of the burden of reading and memorizing so much information by placing that burden within modern computers and to reduce the cost of and enhance the efficiency in maintenance of complex electronic equipment.
A further object of the invention is to provide an integrated modular diagnostic and test work station of universal application, capable of use with many different kinds of electronic equipment and capable of testing digital, analog and RF circuits in electronic equipment.
An additional object is to provide intelligent test workstations that assist and ease the diagnostic burden on factory test personnel and on field technicians.
A still further object of the invention is to provide a more reliable and expeditious means of transferring technical knowledge relating to repair and testing of complex electronic equipment from the factory to the field.
A still additional object is to insure accuracy of measured results by providing for an automatic calibration and normalization of the test equipment and associated circuits.
Another object of the invention is to provide an improved manufacturing system in which test stations may incorporate smaller capacity computers for controlling testing while sharing a larger capacity computer that libraries large volumes of programs and information and functions as the focal point for interfacing with the main factory computer and in which test backup to failure of a given test station is provided by a capability hierarchy arrangement between the various test stations and test cells.